Differential hardmasks for modulation of electrobucket sensitivity

ABSTRACT

Approaches based on differential hardmasks for modulation of electrobucket sensitivity for semiconductor structure fabrication, and the resulting structures, are described. In an example, a method of fabricating an interconnect structure for an integrated circuit includes forming a hardmask layer above an inter-layer dielectric (ILD) layer formed above a substrate. A plurality of dielectric spacers is formed on the hardmask layer. The hardmask layer is patterned to form a plurality of first hardmask portions. A plurality of second hardmask portions is formed alternating with the first hardmask portions. A plurality of electrobuckets is formed on the alternating first and second hardmask portions and in openings between the plurality of dielectric spacers. Select ones of the plurality of electrobuckets are exposed to a lithographic exposure and removed to define a set of via locations.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a U.S. National Phase Application under 35U.S.C. § 371 of International Application No. PCT/US2016/068581, filedDec. 23, 2016, entitled “DIFFERENTIAL HARDMASKS FOR MODULATION OFELECTROBUCKET SENSITIVITY,” which designates the United States ofAmerica, the entire disclosure of which is hereby incorporated byreference in its entirety and for all purposes.

TECHNICAL FIELD

Embodiments of the invention are in the field of semiconductorstructures and processing and, in particular, approaches based onunderlying differential hardmasks for modulation of electrobucketsensitivity for semiconductor structure fabrication, and the resultingstructures.

BACKGROUND

For the past several decades, the scaling of features in integratedcircuits has been a driving force behind an ever-growing semiconductorindustry. Scaling to smaller and smaller features enables increaseddensities of functional units on the limited real estate ofsemiconductor chips. For example, shrinking transistor size allows forthe incorporation of an increased number of memory or logic devices on achip, lending to the fabrication of products with increased capacity.The drive for ever-more capacity, however, is not without issue. Thenecessity to optimize the performance of each device becomesincreasingly significant.

Integrated circuits commonly include electrically conductivemicroelectronic structures, which are known in the arts as vias, toelectrically connect metal lines or other interconnects above the viasto metal lines or other interconnects below the vias. Vias are typicallyformed by a lithographic process. Representatively, a photoresist layermay be spin coated over a dielectric layer, the photoresist layer may beexposed to patterned actinic radiation through a patterned mask, andthen the exposed layer may be developed in order to form an opening inthe photoresist layer. Next, an opening for the via may be etched in thedielectric layer by using the opening in the photoresist layer as anetch mask. This opening is referred to as a via opening. Finally, thevia opening may be filled with one or more metals or other conductivematerials to form the via.

In the past, the sizes and the spacing of vias has progressivelydecreased, and it is expected that in the future the sizes and thespacing of the vias will continue to progressively decrease, for atleast some types of integrated circuits (e.g., advanced microprocessors,chipset components, graphics chips, etc.). One measure of the size ofthe vias is the critical dimension of the via opening. One measure ofthe spacing of the vias is the via pitch. Via pitch represents thecenter-to-center distance between the closest adjacent vias.

When patterning extremely small vias with extremely small pitches bysuch lithographic processes, several challenges present themselves,especially when the pitches are around 70 nanometers (nm) or less and/orwhen the critical dimensions of the via openings are around 35 nm orless. One such challenge is that the overlay between the vias and theoverlying interconnects, and the overlay between the vias and theunderlying landing interconnects, generally need to be controlled tohigh tolerances on the order of a quarter of the via pitch. As viapitches scale ever smaller over time, the overlay tolerances tend toscale with them at an even greater rate than lithographic equipment isable to keep up.

Another such challenge is that the critical dimensions of the viaopenings generally tend to scale faster than the resolution capabilitiesof the lithographic scanners. Shrink technologies exist to shrink thecritical dimensions of the via openings. However, the shrink amounttends to be limited by the minimum via pitch, as well as by the abilityof the shrink process to be sufficiently optical proximity correction(OPC) neutral, and to not significantly compromise line width roughness(LWR) and/or critical dimension uniformity (CDU).

Yet another such challenge is that the LWR and/or CDU characteristics ofphotoresists generally need to improve as the critical dimensions of thevia openings decrease in order to maintain the same overall fraction ofthe critical dimension budget. However, currently the LWR and/or CDUcharacteristics of most photoresists are not improving as rapidly as thecritical dimensions of the via openings are decreasing.

A further such challenge is that the extremely small via pitchesgenerally tend to be below the resolution capabilities of even extremeultraviolet (EUV) lithographic scanners. As a result, commonly two,three, or more different lithographic masks may be used, which tend toincrease the costs. At some point, if pitches continue to decrease, itmay not be possible, even with multiple masks, to print via openings forthese extremely small pitches using EUV scanners.

Thus, improvements are needed in the area of via manufacturingtechnologies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a cross-sectional view of a conventional alignedelectrobucket process.

FIG. 1B illustrates a cross-sectional view of a conventional mis-alignedelectrobucket process.

FIG. 1C illustrates a cross-sectional view of a mis-alignedelectrobucket process, in accordance with an embodiment of the presentinvention.

FIGS. 2A-2O illustrate cross-sectional views of various operations in amethod of patterning using electrobuckets with differentiated hardmasks,in accordance with an embodiment of the present invention.

FIG. 3 illustrates a plan view and corresponding cross-sectional viewsof a 2-dimensional structure for patterning using electrobuckets withdifferentiated hardmasks, in accordance with an embodiment of thepresent invention.

FIGS. 4A-4F, illustrate cross-sectional views corresponding to variousoperations in a method of fabricating and using a differentiatedhardmask in an electrobucket process, in accordance with an embodimentof the present invention.

FIGS. 5A-5D illustrate cross-sectional views corresponding to variousoperations in another method of fabricating and using a differentiatedhardmask in an electrobucket process, in accordance with anotherembodiment of the present invention.

FIGS. 6A-6G illustrate cross-sectional views of various operations in amethod of patterning using electrobuckets with differentiated hardmasks,in accordance with an embodiment of the present invention.

FIG. 7 illustrates a cross-sectional view of the structure of FIG. 6Gfollowing metal fill and planarization to provide a metallization layer,in accordance with an embodiment of the present invention.

FIGS. 8A-8I illustrate portions of integrated circuit layersrepresenting various operations in a method of subtractive self-alignedvia patterning using electrobuckets with differentiated hardmasks, inaccordance with another embodiment of the present invention, where:

FIG. 8A illustrates a starting point structure for a subtractive viaprocess following deep metal line fabrication;

FIG. 8B illustrates the structure of FIG. 8A following recessing of themetal lines;

FIG. 8C illustrates the structure of FIG. 8B following formation of aninter-layer dielectric (ILD) layer;

FIG. 8D illustrates the structure f FIG. 8C following deposition andpatterning of a hardmask layer;

FIG. 8E illustrates the structure of FIG. 8D following trench formationdefined using the pattern of the hardmask of FIG. 8D;

FIG. 8F illustrates the structure of FIG. 8E following electrobucketformation in all possible via locations with differentiated hardmasks inalternating locations;

FIG. 8G illustrates the structure of FIG. 8F following via locationselection;

FIG. 8H illustrates the structure of FIG. 8G following conversion of theremaining electrobuckets to permanent ILD material; and

FIG. 8I illustrates the structure of FIG. 8H following metal e and viaformation.

FIG. 9 illustrates a computing device in accordance with oneimplementation of an embodiment of the invention.

FIG. 10 is an interposer implementing one or more embodiments of theinvention.

DESCRIPTION OF THE EMBODIMENTS

Approaches based on underlying differential hardmasks for modulation ofelectrobucket sensitivity for semiconductor structure fabrication, andthe resulting structures, are described. In the following description,numerous specific details are set forth, such as specific integrationand material regimes, in order to provide a thorough understanding ofembodiments of the present invention. It will be apparent to one skilledin the art that embodiments of the present invention may be practicedwithout these specific details. In other instances, well-known features,such as integrated circuit design layouts, are not described in detailin order to not unnecessarily obscure embodiments of the presentinvention. Furthermore, it is to be understood that the variousembodiments shown in the Figures are illustrative representations andare not necessarily drawn to scale.

Certain terminology may also be used in the following description forthe purpose of reference only, and thus are not intended to be limiting.For example, terms such as “upper,” “lower,” “above,” “below,” “bottom,”and “top” refer to directions in the drawings to which reference ismade. Terms such as “front,” “back,” “rear,” and “side” describe theorientation and/or location of portions of the component within aconsistent but arbitrary frame of reference which is made clear byreference to the text and the associated drawings describing thecomponent under discussion. Such terminology may include the wordsspecifically mentioned above, derivatives thereof, and words of similarimport.

One or more embodiments described herein is directed to electrobucketunderlying hardmask “colors” that differentiate electrobucketperformance. Applications may be directed toward one or more of electronbeam (e-beam) lithography, extreme ultra-violet (EUV) lithography,general lithography applications, solutions for overlay issues (such asedge placement error, EPE), and general photoresist technologies. In anembodiment, materials are described that are suitable for improvingperformance of so-called “ElectroBucket” based approaches. In such anapproach, a resist material is confined to a pre-patterned hardmask.Select ones of the electrobuckets are then removed using ahigh-resolution lithography tool, e.g., an e-beam or EUV lithographytool. Specific embodiments include use of materials and process flows tosolve issues associated with unwanted via openings caused bylithographic critical dimension (CD) and/or overlay errors. Approachesdescribed herein may be described as involving alternating anddifferentiated underlying hardmask technology.

To provide context, current fabrication techniques for vias involve a“blind” process in which a via opening is patterned in a stack far abovean ILD trench. The via opening pattern is then etched deep down into thetrench. Overlay errors accumulate and can cause various problems, e.g.,shorts to neighboring metal lines. In an example, patterning andaligning of features at less than approximately 50 nanometer pitchrequires many reticles and critical alignment strategies that areotherwise extremely expensive for a semiconductor manufacturing process.In an embodiment, by contrast, approaches described herein enablefabrication of self-aligned conductive vias, greatly simplifying the webof overlay errors, and leaving only one critical overlay step (Mx+1grating). In an embodiment, then, offset due to conventionallithograph/dual damascene patterning that must otherwise be tolerated,is not a factor or is less of a factor for the resulting structuresdescribed herein.

To provide further context, a conventional resist electrobucketstructure following electrobucket development may only partially clearafter a mis-aligned exposure. Using a broader exposure window can ensurecomplete clearance of the selected electrobucket, but increases the riskof exposing non-selected neighboring electrobuckets. Thus, usingconventional approaches, constraints regarding exposure size andmisalignment tolerance are tight to avoid, if possible, either onlypartially cleared selected electrobuckets with some residual photoresistremaining or opening of non-selected electrobucket potentially leadingto subsequent formation of conductive structures in unwanted locations.

More particularly, electrobuckets can be formed by fabricating “buckets”from a 2-dimensional grating to confine photoresist. The confinedbuckets of photoresist are then selectively exposed depending on whereit is preferred to either keep or dissolve the photoresist. Onechallenge is the edge placement error control of such a patterningscheme. For example, if the electron beam is mis-aligned with respect tothe bucket, then there is a risk of opening an unwanted bucket adjacentto the desired bucket.

By way of a first example, FIG. 1A illustrates a cross-sectional view ofa conventional aligned electrobucket process. A plurality ofelectrobuckets 102 of photoresist is confined among “bucket” features104 over a hardmask layer 106. An aligned e-beam or EUV exposure 108 ofa select electrobucket location 110 is performed. Subsequently, theselected electrobucket 110 is opened upon development and removal of theselected and exposed photoresist in the location 110. The result of suchan aligned process is the opening of a selected electrobucket at theselected location 110.

By way of a second example, FIG. 1B illustrates a cross-sectional viewof a conventional mis-aligned electrobucket process. A plurality ofelectrobuckets 122 of photoresist is confined among bucket features 124over a hardmask layer 126. A mis-aligned e-beam or EUV exposure 128 of aselect electrobucket location 130 is performed. Subsequently, theselected electrobucket 130 is opened upon development and removal of theselected and exposed photoresist in the location 130. However,inadvertently, a neighboring electrobucket at location 132 is alsoopened because of the mis-alignment and resulting exposure bymis-aligned e-beam or EUV exposure 128. Accordingly, in addition to adesired electrobucket location 130, an unselected or undesiredelectrobucket is also opened at location 132.

Addressing one or more of the issues raised in the description of FIG.1B, in accordance with one or more embodiments of the present invention,electrobucket approaches described herein involve the “coloring”hardmasks of adjacent buckets to change the sensitivity of theelectrobucket. For example, some materials have more backscatter andgenerate more secondary electrons than other materials. By increasingthe sensitivity of the desired bucket relative to the undesired bucket,reduce the risk of the undesired bucket opening due to mis-alignment ofthe electron beam with respect to the buckets can be reduced.

By way of example of a differentiated approach. FIG. 1C illustrates across-sectional view of a mis-aligned electrobucket process, inaccordance with an embodiment of the present invention. A plurality ofelectrobuckets 142 of photoresist is confined among bucket features 144over a hardmask layer 146. The hardmask 146 is differentiated in that itincludes first hardmask portions 146A and second hardmask portions 146B.The materials of first hardmask portions 146A and second hardmaskportions 146B, respectively, may differ in the extent of reaction to anexposure which effectively alters the performance of respectiveelectrobuckets formed thereon.

Referring again to FIG. 1C, a mis-aligned e-beam or EUV exposure 148 ofa select electrobucket location 150 is performed. Subsequently, theselected electrobucket 150 is opened upon development and removal of theselected and exposed photoresist in the location 150. However, althougha neighboring electrobucket at location 152 is also exposed tomis-aligned e-beam or EUV exposure 128, the electrobucket at location152 is not removed upon development of the electrobuckets. In anembodiment, the electrobuckets 142 on second hardmask portions 146B aremore sensitive to an e-beam or EUV exposure by the underlying secondhardmask portions 146B versus the neighboring or alternatingelectrobuckets 142 on first hardmask portions 146B. Accordingly, in theend, only the desired electrobucket location 150 is opened, while theunselected or undesired electrobucket (albeit exposed electrobucket) atlocation 152 is not opened. Thus, increased edge placement errortolerance and reduced risk of undesired bucket opening may be achieved.

Referring again to FIG. 1C, in an embodiment, the second hardmaskportions 146B are rendered or modified to provide electrobuckets thereonwith greater sensitivity to e-beam or EUV exposure as compared toelectrobuckets formed on the first hardmask portions 146A. In anotherembodiment, the first hardmask portions 146A are rendered or modified toprovide electrobuckets thereon with less or reduced sensitivity toe-beam or EUV exposure as compared to electrobuckets formed on thesecond hardmask portions 146B. In either case, in an embodiment, thesecond hardmask portions 146B provide for increased backscatter and thegeneration of more secondary electrons into electrobuckets thereonversus the backscatter and the generation of more secondary electronsprovided by first hardmask portions 146A.

In accordance with an embodiment of the present invention, approachesdescribed herein involve differentiated hardmask fabrication underlyingelectrobuckets to increase reactivity of areas of wanted vias and/or toslow down areas of unwanted vias in contrast to existingstate-of-the-art approaches, fabrication schemes described hereininvolve the fundamentally different approach of using a selectivebottom-up electrobucket differentiation methodology. By employing such aselective bottom-up electrobucket differentiation methodology, the needfor self-enclosed via structures which otherwise take up metal CDmargins may be mitigated. In specific embodiments, processes describedherein are more tolerant to edge-placement errors, in which an aerialimage does not perfectly align to an electrobucket grid. As a result,the selected locations are ultimately cleared to provide openelectrobucket locations following development. The non-selectedlocations which may also receive some exposure remain as closedelectrobucket locations following development.

As an exemplary process scheme, FIGS. 2A-2O illustrate cross-sectionalviews of various operations in a method of patterning usingelectrobuckets with differentiated hardmasks, in accordance with anembodiment of the present invention.

Referring to FIG. 2A, a starting structure 200 for a method ofpatterning using electrobuckets includes a second hardmask layer 208formed on a first hardmask layer 206 formed on or above an inter-layerdielectric (ILD) layer 204 formed above a substrate 202.

Referring to FIG. 2B, the second hardmask layer 208 is patterned toprovide a plurality of backbone features 210.

Referring to FIG. 2C, a plurality of hardmask spacers 212 is formedalong the sidewalls of the backbone features 210. The plurality ofhardmask spacers 212 may be fabricated using a conformal deposition andsubsequent anisotropic etching process. The structure of FIG. 2C may beviewed as including a grating structure of the plurality of hardmaskspacers 212. In an embodiment, the grating structure includes theplurality of hardmask spacers 212 patterned using a pitch divisionpatterning scheme, such as a pitch halving or a pitch quartering processscheme, using the plurality of backbone features 210 as a template ofmandrel.

Referring to FIG. 2D, the first hardmask layer 206 is patterned to formfirst hardmask portions 214. In an embodiment, the first hardmask layer206 is patterned using an etch process as masked by the plurality ofhardmask spacers 212 and the backbone features 210.

Referring to FIG. 2E, second hardmask portions 216 are formed betweenand laterally adjacent to the first hardmask portions 214. The firsthardmask portions 214 and the second hardmask portions 216 together forma differentiated hardmask 218. In one embodiment, the first hardmaskportions 214 and the second hardmask portions 216 have substantially thesame thickness, as is depicted in FIG. 2E. In other embodiments, thefirst hardmask portions 214 differ in thickness from the second hardmaskportions 216.

In an embodiment, the second hardmask portions 216 are formed using adeposition and etch back process to leave second hardmask portions 216remaining. In another embodiment, the second hardmask portions 216 areformed using a selective deposition or growth process. In one suchembodiment, selective deposition or growth is achieved by firstspinning-on material over the entire structure of FIG. 2D and then“washing away” material that does not adhere to the exposed portions ofILD layer 204. In another embodiment, selective deposition or growth isperformed only on the exposed portions of ILD layer 204 using a chemicalvapor deposition (CVD) or atomic layer deposition (ALD) process. Whethera blanket deposition and etch process or a selective deposition orgrowth process is used, in an embodiment, the second hardmask portions216 are ultimately only formed between alternating pairs of neighboringspacer features 212 and not between each pair of spacer features 212(i.e., at locations 110).

Referring to FIG. 2F, the plurality of backbone features 210 is removedfrom the structure of FIG. 2E. In an embodiment, the plurality ofbackbone features 210 is removed using a wet etch selective to thematerials of the hardmask spacers 212, the first hardmask portions 214and the second hardmask portions 216. In another embodiment, theplurality of backbone features 210 is removed using a dry or plasma etchselective to the materials of the hardmask spacers 212, the firsthardmask portions 214 and the second hardmask portions 216.

Referring to FIG. 2G, a photoresist layer 220 is formed over thestructure of FIG. 2F to form a plurality of electrobuckets. In anembodiment, the photoresist layer 220 is formed within and is confinedby the hardmask spacers 212. In one such embodiment, the uppermostsurface of the photoresist layer 220 is below an uppermost surface ofthe hardmask spacers 212, as is depicted. Alternating ones of theelectrobuckets formed by deposition of the photoresist layer 220 areformed above the first hardmask portions 214 of differentiated hardmask218, while remaining ones of the electrobuckets formed by deposition ofthe photoresist layer 220 are formed above the second hardmask portions216 of differentiated hardmask 218.

In an embodiment the photoresist layer 220 is formed over the structureof FIG. 2F using a spin-on process. In an embodiment, the photoresistlayer 220 has a photolyzable composition. In one such embodiment, thephotolyzable composition includes an acid-deprotectable photoresistmaterial. In an embodiment, a photo-acid generator (PAG) component isincluded and, in a specific embodiment, includes a material selectedfrom the group consisting of triethyl, trimethyl and othertrialkylsulfonates, where the sulfonate group is selected from the groupconsisting of trifluoromethylsulfonate, nonanfluorobutanesulfonate, andp-tolylsulfonate, or other examples containing —SO3 sulfonate anionbound to organic group. In an embodiment, the acid-deprotectablephotoresist material is an acid-deprotectable material selected from thegroup consisting of a polymer, a molecular glass, a carbosilane and ametal oxide. In an embodiment, the acid-deprotectable photoresistmaterial includes a material selected from the group consisting of apolyhydroxystyrene, a polymethacrylate, small molecular weight molecularglass versions of a polyhydroxystyrene or a polymethacrylate whichcontain ester functionality sensitive to acid-catalyzed deprotection tocarboxylic acid, a carbosilane, and a metal oxide possessingfunctionality sensitive to acid catalyzed deprotection or cross-linking.In another embodiment, the photolyzable material is not a photo-acidgenerator (PAG)-based photolyzable material. In an embodiment, thephotolyzable material is a positive tone material. In anotherembodiment, the photolyzable material is a negative tone material.

Referring to FIG. 2H, an electrobucket selection process involvesexposing a portion of the structure of FIG. 2G to a lithography exposure222. In an embodiment, the lithography exposure 222 is performed using arelatively large exposure window. For example, in one embodiment, alocation 224 is selected as a via location for ultimate electrobucketclearance. Neighboring electrobucket locations 226 represent locationsthat may be otherwise be exposed and cleared by a large exposure windowand/or by a mis-aligned exposure window. However, even though theelectrobucket locations 226 may be exposed by lithography exposure 222,they are not opened upon eventual development because they are formed onthe first hardmask portions 214 and not on the second hardmask portions216.

In an embodiment, the lithography exposure 222 involves exposing thestructure to e-beam radiation or extreme ultraviolet (EUV) radiation. Inan embodiment, the radiation has a wavelength approximately 13.5nanometers. In another embodiment, the radiation has an energy in therange of 5-150 keV. In an embodiment, radiation has an energy having awavelength of approximately 365 nanometers.

In an embodiment, the second hardmask portions 216 are rendered ormodified to provide electrobuckets thereon with greater sensitivity toe-beam or EUV exposure as compared to electrobuckets formed on the firsthardmask portions 214. In another embodiment, the first hardmaskportions 214 are rendered or modified to provide electrobuckets thereonwith less or reduced sensitivity to e-beam or EUV exposure as comparedto electrobuckets formed on the second hardmask portions 216. In eithercase, in an embodiment, the second hardmask portions 216 provide forincreased backscatter and the generation of more secondary electronsinto electrobuckets thereon versus the backscatter and the generation ofmore secondary electrons provided by first hardmask portions 214.

In an embodiment, subsequent to the lithography exposure 222, a bakeoperation is performed. In one such embodiment, the bake is performed ata temperature approximately in the range of 50-120 degrees Celsius for aduration of approximately in the range of 0.5-5 minutes. The structuremay then be subjected to a development process. The development processclears the exposed electrobucket 222 at location 224 (but not atlocations 226). In an embodiment, the neighboring electrobuckets atlocations 226 do not clear upon development even though at leastportions of the photoresist layer 220 in those locations may have beenexposed to the lithography exposure 222.

In an embodiment, developing the structure of FIG. 2H includes, in thecase of positive tone development, immersion or coating with standardaqueous TMAH developer (e.g., in a concentration range from 0.1M-1M) orother aqueous or alcoholic developer based on tetraalkylammoniumhydroxides for 30-120 seconds followed by rinse with deionized (DI)water. In another embodiment, in the case of negative tone development,developing the structure includes immersion or coating with organicsolvents such as cyclohexanone, 2-heptanone, propylene glycolmethylethyl acetate or others followed by rinse with another organicsolvent such as hexane, heptane, cyclohexane or the like.

Referring to FIG. 2I, using the remaining electrobuckets of photoresistlayer 220 as a mask, the region of the second hardmask portion 216 ofthe differentiated hardmask 218 is removed from location 224 to providea selected via location 227 in a once-patterned differentiated hardmask218′ above the now partially exposed ILD layer 204. The remainingelectrobuckets of photoresist layer 220 are then removed. In anembodiment, the region of the second hardmask portion 216 of thedifferentiated hardmask 218 is removed from location 224 using aselective wet etch or dry or plasma etch process. The remainingelectrobuckets of photoresist layer 220 are then removed using an ashprocess.

At this stage, with a selected via location 227 formed in theonce-patterned differentiated hardmask 218′, the once-patterneddifferentiated hardmask 218′ can be used as a via patterning mask forforming line and/or via trenches in the ILD layer 204, akin to thepatterning described below in association with FIG. 2N. However, it maybe the case than a second via selection process is performed prior topatterning the ILD layer 204, as is described below in association withFIGS. 2J-2M.

Referring to FIG. 2J, the remaining second hardmask portions 216 of theonce-patterned differentiated hardmask 218′ are modified to providemodified second hardmask portions 228. In an embodiment, the modifiedsecond hardmask portions 228 provide for less reactive electrobucketsthan provided for by the second hardmask portions 216. In one suchembodiment, the remaining second hardmask portions 216 of theonce-patterned differentiated hardmask 218′ are modified by an approachdescribed below in association with FIGS. 4A-4E or with FIGS. 5A-5D.

Referring to FIG. 2K, a photoresist layer 230 is formed over thestructure of

FIG. 2J to form a plurality of electrobuckets. In an embodiment, thephotoresist layer 230 is formed within and is confined by the hardmaskspacers 212. In one such embodiment, the uppermost surface of thephotoresist layer 230 is below an uppermost surface of the hardmaskspacers 212, as is depicted. Alternating ones of the electrobucketsformed by deposition of the photoresist layer 230 are formed above thefirst hardmask portions 214, while remaining ones of the electrobucketsformed by deposition of the photoresist layer 220 are formed above themodified second hardmask portions 228, with the exception of oneelectrobucket 232 formed at selected via location 227. In an embodiment,the photoresist layer 230 is the same as or similar to the photoresistlayer 220 described above.

Referring to FIG. 2L, a second electrobucket selection process involvesexposing a portion of the structure of FIG. 2K to a lithography exposure234, which may be similar to the lithography exposure 222 describedabove. In an embodiment, the lithography exposure 234 is performed usinga relatively large exposure window. For example, in one embodiment, alocation 236 is selected as a via location for ultimate electrobucketclearance. Neighboring electrobucket location 238 represents a locationthat may be otherwise be exposed and cleared by a large exposure windowand/or by a mis-aligned exposure window. However, even though theelectrobucket location 238 may be exposed by lithography exposure 234,it is not opened upon eventual development because it is formed on amodified second hardmask portion 228 and not on a first hardmask portion214.

In an embodiment, the modified second hardmask portions 228 are renderedor modified to provide electrobuckets thereon with less or reducedsensitivity to e-beam or EUV exposure as compared to electrobucketsformed on the first hardmask portions 214. In another embodiment,however, the first hardmask portions 214 are rendered or modified toprovide electrobuckets thereon with greater sensitivity to e-beam or EUVexposure as compared to electrobuckets formed on the modified secondhardmask portions 228. In either case, in an embodiment, the firsthardmask portions 214 provide for increased backscatter and thegeneration of more secondary electrons into electrobuckets thereonversus the backscatter and the generation of more secondary electronsprovided by modified second hardmask portions 228. In an embodiment, theelectrobucket at location 236 is developed as described above forelectrobucket development at location 224.

Referring to FIG. 2M, using the remaining electrobuckets of photoresistlayer 230 as a mask, the region of the first hardmask portion 214 isremoved from location 236 to provide a selected via location 237 in atwice-patterned differentiated hardmask 218″ above the twice partiallyexposed ILD layer 204. The remaining electrobuckets of photoresist layer230 are then removed. In an embodiment, the region of the first hardmaskportion 214 is removed from location 236 using a selective wet etch ordry or plasma etch process. The remaining electrobuckets of photoresistlayer 230 are then removed using an ash process. At this stage, in anembodiment, via selection is complete.

Referring to FIG. 2N, the structure of FIG. 2M is exposed to an etchprocess used to form trenches 238 in a patterned dielectric layer 204′.In one embodiment, the trenches 238 represent eventual interconnect linelocations each having an associated underlying via. Accordingly, theetch process used to form trenches 238 is, in one embodiment, a viaopening process based on selection and removal of one or moreelectrobuckets.

Referring to FIG. 2O, conductive lines and vias are fabricated. In anembodiment, conductive lines and vias are fabricated by removingremaining portions of the twice-patterned differentiated hardmask 218″not covered by the hardmask spacers 212. Conductive line trenches 240are then formed in the patterned dielectric layer 204′ to formtwice-patterned dielectric layer 204″. The hardmask spacers 212 and anyremaining portions of the twice-patterned differentiated hardmask 218″are then removed. Subsequently, metal lines 242 and conductive vias 244are formed in the twice-patterned dielectric layer 204″, e.g., by ametal deposition and planarization process.

In either case, whether one or two via selection operations areperformed, the structure of FIG. 2O, or like structures, may then beused as a foundation for forming subsequent metal line/via and ILDlayers. Alternatively, the structure of FIG. 2O, or like structures, mayrepresent the final metal interconnect layer in an integrated circuit.It is to be appreciated that the above process operations may bepracticed in alternative sequences, not every operation need beperformed and/or additional process operations may be performed.

It is to be appreciated that the process scheme described in associationwith FIGS. 2A-2O may represent a one-dimensional (1D) or atwo-dimensional (2D) electrobucket approach. For example, in a 1Delectrobucket approach, lines of the grating structure of hardmaskspacers 212 extend without interruption over a long region. By contrast,in a 2D electrobucket approach, lines of such a grating structure may beinterrupted at intervals at approximately the same pitch as the pitch ofthe lines of the grating structure of hardmask spacers 212.

As an example of a 2D electrobucket approach. FIG. 3 illustrates a planview and corresponding cross-sectional views of a 2-dimensionalstructure for patterning using electrobuckets with differentiatedhardmasks, in accordance with an embodiment of the present invention.

Referring to FIG. 3, the cross-sectional view taken along the a-a′ axisrepresents a similar cross-section view of FIG. 2F. However, as seen inthe plan view and the corresponding cross-sectional view taken along theb-h′ axis of FIG. 3, a cross-grating structure 300 is formed atintervals along the grating structure of hardmask spacers 212. In oneembodiment, the cross-grating structure 300 is a hardmask layer thateffectively confines electrobucket locations at intervals along thegrating structure of hardmask spacers 212. In an embodiment, thestructure of FIG. 3 is subjected to operations described in associationwith FIG. 2D and on to form vias that have locations confined in twodimensions.

In an embodiment, whether a 1D or 2D approach is used, approachesdescribed herein involve the fabrication of regular structures coveringall possible feature locations, such as all possible via locations,followed by selective patterning of only the desired or select features.In an embodiment, first or second hardmask material portions remain inthe final structure at the corners of metal lines underneath anymis-landed vias.

As described briefly above, a hardmask portion can be changed from amore sensitive material to a less sensitive material. In a particularembodiment, a hardmask material is initially “stuffed” (e.g., a porouscarbon doped oxide stuffed with titanium nitride, TiN), and thensubsequently “de-stuffed.” In an exemplary processing scheme. FIGS.4A-4E illustrate cross-sectional views corresponding to variousoperations in a method of fabricating and using a differentiatedhardmask in an electrobucket process, in accordance with an embodimentof the present invention.

Referring to FIG. 4A, a starting structure such as the structure of FIG.2F can include an initially porous hardmask portion 216. The poroushardmask portion 216 has a plurality of pores formed therein.

In an embodiment, the porous hardmask portion 216 is a low-k porousdielectric material layer. In an embodiment, the porous hardmask portion216 is formed using a spin-on deposition process. In an embodiment, theporous dielectric material is a highly porous, e.g., 50%, spin-onmaterial that has been optimized to fill high aspect ratio features. Inan embodiment, the porous dielectric material has 30% or more poredensity. In one such embodiment, the porous dielectric material has aporosity approximately in the range of 40-60%, and preferably around50%. In an embodiment, the pores are open cells pores in that they areinterconnected and are not closed cell pores.

In an embodiment, the porous dielectric material is selected from aclass of materials based on hydrosilane precursor molecules, wherecatalyst mediates reaction of Si—H bonds with cross-linkers such aswater, tetraethoxyorthosilicate (TEOS), hexaethoxytrisilacyclohexane orsimilar multifunctional cross-linkers. In one such embodiment, theporous dielectric material is based on trisilacyclohexanes linkedtogether by O groups. In other embodiments, alkoxy-silane baseddielectric precursors or silsesquioxane (SSQ) are used to form theporous dielectric material. Although not limited to such material, in anembodiment, the porous dielectric material is a spin-on dielectricmaterial based on a 1,3,5-trisilacyclohexane building block.Cross-linking with loss of solubility of such a material (or othersilicon based dielectrics) can be initiated either thermally, or atlower temperatures, by use of acid, base or Lewis acid catalystprocesses. In one embodiment, such low temperature catalysis is criticalfor the implementation of approaches described herein.

Referring to FIG. 4B, a loading process 400 is used to fill the pores ofthe porous hardmask portion 216 to form a pore-filled hardmask portion216′. In an embodiment, the pore-filled hardmask portion 216′ hasincreased response to e-beam or EUV lithography to enhance electrobucketsensitivity.

In an embodiment, the pores of the porous dielectric material are filledusing an atomic layer deposition (ALD) process. In one such embodiment,a slow and penetrating ALD process is used to fill the pores of theporous dielectric material. By using the above described two-operationprocess of spin-on deposition followed by ALD pore filling, chemicalstability of the resulting pore-filled material may be achieved. Inother embodiments, the pores of the porous dielectric material arefilled using a second spin-on process.

In an embodiment, the pores of the porous dielectric material are filledwith a metal-containing material. In one such embodiment, themetal-containing material is a metal nitride such as, but not limitedto, titanium nitride (TiN) or tantalum nitride (TaN). In another suchembodiment, the metal-containing material is a metal oxide such as, butnot limited to, tantalum oxide (Ta₂O₅), titanium oxide (TiO₂), aluminumoxide (Al₂O₃), or hafnium oxide (HfO₂).

Referring to FIG. 4C, a photoresist layer 402 of electrobuckets is usedto pattern a via location 404 by a process such as described above inassociation with FIGS. 2G-2I.

Referring to FIG. 4D, the material used to fill or “stuff” the pores toform pore-filled hardmask portion 216′ are removed by a process 406,such as an evaporation or sublimation process.

Referring to FIG. 4E, a second photoresist layer 408 of electrobucketsis used to pattern a second via location 410 over a differentiatedhardmask portion 214. In an embodiment, the second via location 410 isformed by a process such as described above in association with FIGS. 2Kand 2L.

In another particular embodiment, a hardmask portion is intentionallyoxidized or reduced to change its electron backscatter/secondaryelectron generator properties. As an example, FIGS. 5A-5D illustratecross-sectional views corresponding to various operations in anothermethod of fabricating and using a differentiated hardmask in anelectrobucket process, in accordance with another embodiment of thepresent invention.

Referring to FIG. 5A, a starting structure such as the structure of FIG.2F can include an initially metallic hardmask portion 216.

Referring to FIG. 5B, a photoresist layer 500 of electrobuckets is usedto pattern a via location 502 by a process such as described above inassociation with FIGS. 2G-2I.

Referring to FIG. 5C, an oxidation process 504 is used to form oxidizedhardmask portions 216 from metallic hardmask portions 216.

Referring to FIG. 5D, a second photoresist layer 506 of electrobucketsis used to pattern a second via location 508 over a differentiatedhardmask portion 214. In an embodiment, the second via location 508 isformed by a process such as described above in association with FIGS. 2Kand 2L.

In an exemplary embodiment, approaches described above build onapproaches using so-called “electrobuckets,” in which every possiblefeature, e.g. via, is pre-patterned into a substrate. Then, aphotoresist is filled into patterned features and the lithographyoperation is merely used to choose select vias for via openingformation. In a particular embodiment described below, a lithographyoperation is used to define a relatively large hole above a plurality ofelectrobuckets that include photoresist and differentiated hardmaskportions in alternating photoresist locations, as described above. Sucha colored underlying hardmask photoresist electrobucket approach may beimplemented to allow for larger critical dimensions (CD)s and/or errorsin overlay while retaining the ability to choose the via of interest.

In general, one or more embodiments are directed to an approach thatemploys a subtractive technique to ultimately form conductive vias and,possibly, non-conductive spaces or interruptions between metals(referred to as “plugs”). Vias, by definition, are used to land on aprevious layer metal pattern. In this vein, embodiments described hereinenable a more robust interconnect fabrication scheme since alignment bylithography equipment is no longer relied on. Such an interconnectfabrication scheme can be used to save numerous alignment/exposures, canbe used to improve electrical contact (e.g., by reducing viaresistance), and can be used to reduce total process operations andprocessing time otherwise required for patterning such features usingconventional approaches.

Applications of approaches described herein may be implemented to createregular structures covering all possible via (or plug) locations,followed by selective patterning of only the desired features. Morespecifically, one or more embodiments described herein involves the useof a subtractive method to pre-form every via or via opening using thetrenches already etched. An additional operation is then used to selectwhich of the vias and plugs to retain. As described above, suchoperations can be illustrated using “electrobuckets,” although theselection process may also be performed using a more conventional resistexpose and ILD backfill approach.

In another aspect, a differentiated hardmask process is performed usingtwo distinct photoresist deposition process, even though the samephotoresist material may be deposited in both distinct operations. Sucha two-operation photoresist approach may be used to direct or confinethe effects of a differentiated hardmask material at alternatinglocations in that a break is provided between the photoresist materialat neighboring locations. As an example, FIGS. 6A-6G illustratecross-sectional views of various operations in a method of patterningusing electrobuckets with differentiated hardmasks, in accordance withan embodiment of the present invention.

FIG. 6A illustrates a cross-sectional view of a starting structure 600following deposition, but prior to patterning, of a first hardmaskmaterial layer 604 formed on an interlayer dielectric (ILD) layer 602,in accordance with an embodiment of the present invention. Referring toFIG. 6A, a patterned mask 606 has spacers 608 formed along sidewallsthereof, on or above the first hardmask material layer 604.

FIG. 6B illustrates the structure of FIG. 6A following first timepatterning of the first hardmask layer and subsequent firstelectrobucket till, in accordance with an embodiment of the presentinvention. Referring to FIG. 6B, the patterned mask 606 andcorresponding spacers 608 are used together as a mask during an etch toform trenches 610 through the first hardmask material layer 604 andpartially into the ILD layer 602. The trenches 610 are then filled withfirst hardmask portions 697 and first electrobuckets 612 which include aphotoresist material.

FIG. 6C illustrates the structure of FIG. 6B following second timepatterning of the first hardmask layer and subsequent secondelectrobucket fill, in accordance with an embodiment of the presentinvention. Referring to FIG. 6C, the patterned mask 606 is removed and asecond plurality of trenches 614 is etched through the first hardmaskmaterial layer 604 and partially into the ILD layer 602, between spacers608. Subsequently, the trenches 614 are filled with second hardmaskportions 699 and second electrobuckets 618 which include a photoresistmaterial. In one such embodiment, the second electrobuckets 618 and thefirst electrobuckets 612 are filled with the same photoresist material.

In an embodiment, the first hardmask portions 697 are rendered ormodified to provide electrobuckets thereon with greater sensitivity toe-beam or EUV exposure as compared to electrobuckets formed on thesecond hardmask portions 699. In another embodiment, the second hardmaskportions 699 are rendered or modified to provide electrobuckets thereonwith less or reduced sensitivity to e-beam or EUV exposure as comparedto electrobuckets formed on the first hardmask portions 697. In eithercase, in an embodiment, the first hardmask portions 697 provide forincreased backscatter and the generation of more secondary electronsinto electrobuckets thereon versus the backscatter and the generation ofmore secondary electrons provided by second hardmask portions 699.

Referring again to FIG. 6C, the negative pattern of the spacers 608 isthus transferred, e.g., by two etch processes forming trenches 610 and614, to the first hardmask material layer 604. In one such embodiment,the spacers 608 and, hence, the trenches 610 and 614 are formed with agrating pattern, as is depicted in FIG. 6C. In an embodiment, thegrating pattern is a tight pitch grating pattern. In a specific suchembodiment, the tight pitch is not achievable directly throughconventional lithography. For example, a pattern based on conventionallithography may first be limited to mask 606, but the pitch may behalved by the use of negative spacer mask patterning, as is depicted inFIGS. 6A-6C. Even further, although not shown, the original pitch may bequartered by a second round of spacer mask patterning. Accordingly, thegrating-like pattern of the electrobuckets 612 and 618, collectively, isspaced at a constant pitch and has a constant width.

FIG. 6D illustrates the structure of FIG. 6C following planarization toisolate the first and second electrobuckets from one another, inaccordance with an embodiment of the present invention. Referring toFIG. 6D, the second electrobuckets 618 and the top portions of thespacers 608 are planarized, e.g., by chemical mechanical polishing(CMP), until the top surfaces of the first electrobuckets 612 areexposed, forming discrete second electrobuckets 618. In one embodiment,the combination of first electrobuckets 612 and second electrobuckets618 represent all possible via locations in a subsequently formedmetallization structure. One of the first electrobuckets 612 is labeledas 612A to indicate that it is selected from removal for ultimate viafabrication.

FIG. 6E illustrates the structure of FIG. 6D following exposure anddevelopment of two electrobuckets to leave selected via locations, inaccordance with an embodiment of the present invention. Referring toFIG. 6E, a second hardmask 620 is formed and patterned on the structureof FIG. 6D. The patterned second hardmask 620 reveals two of the firstelectrobuckets 612. The selected electrobuckets are exposed to lightirradiation, such as an e-beam or EUV exposure 621. It is to beappreciated that description herein concerning forming and patterning ahardmask layer involves, in an embodiment, mask formation above ablanket hardmask layer. The mask formation may involve use of one ormore layers suitable for lithographic processing. Upon patterning theone or more lithographic layers, the pattern is transferred to thehardmask layer by an etch process to provide a patterned hardmask layer.

In accordance with one embodiment, referring again to FIG. 6E,neighboring one of the second electrobuckets 618 are partially exposed,e.g., due to mis-alignment in the patterning of second hardmask 620. Inparticular, two of the second electrobuckets 618 are inadvertentlyexposed at regions 650, even though they have not been selected aslocations for via fabrication. Thus, the selected ones of the firstelectrobuckets 612 are exposed to the EUV or e-beam radiation to agreater extent than the neighboring partially exposed ones of the secondelectrobuckets 618. Subsequent to exposing the structure to EUV ore-beam radiation 621, a first bake of the electrobuckets is performed.Subsequent to performing the first bake, the structure is exposed toultraviolet (UV) radiation. In one embodiment, the mask 620 remainsduring the UV radiation and is then subsequently removed. However, inanother embodiment, the mask 620 is first removed and the electrobucketsare then all exposed to the UV radiation to approximately the sameextent. In either case, subsequent to exposing the structure to UVradiation, a second bake of the electrobuckets is performed.

Referring again to FIG. 6E, the electrobuckets are subjected to adevelop process. During the develop process, the select one of the firstelectrobuckets 612 targeted for via fabrication are emptied in that thephotoresist is removable. However, locations not selected for viafabrication, including the ones of the second electrobuckets 618 thatwere partially exposed at regions 650, are not opened during the developprocess, in that the resist material is not removable in the developprocess because of the second hardmask portions 699, as described above.The developing provides selected via openings 613A.

FIG. 6F illustrates the structure of FIG. 6E following etching to formvia locations, in accordance with an embodiment of the presentinvention. Referring to FIG. 6F, the pattern of the via openings 613Aare subjected to a selective etch process, such as a selective plasmaetch process, to extend the via openings deeper into the underlying ILDlayer 602, forming via patterned ILD layer 602′ with via locations 624.The etching is selective to remaining electrobuckets 612 and 618 and tothe spacers 608.

FIG. 6G illustrates the structure of FIG. 6F in preparation for metalfill, in accordance with an embodiment of the present invention.Referring to FIG. 6G, all remaining first and second electrobuckets 612and 618 are removed. The remaining first and second electrobuckets 612and 618 may be removed directly, or may first be exposed and developedto enable removal. The removal of the remaining first and secondelectrobuckets 612 and 618 provides metal line trenches 626, some ofwhich are coupled to via locations 624 in patterned ILD layer 602′.

FIG. 7 illustrates a cross-sectional view of the structure of FIG. 6Gfollowing metal fill and planarization to provide a metallization layer,in accordance with an embodiment of the present invention. Referring toFIG. 7, subsequent processing can include removal of spacers 608 andhardmask layer 604, and metal fill of metal line trenches 626 and vialocations 624 to form conductive metal lines 700 and conductive vias702, respectively. In one such embodiment, metallization is formed by ametal fill and polish back process. The structure of FIG. 7 maysubsequently be used as a foundation for forming subsequent metalline/via and ILD layers. Alternatively, the structure of FIG. 7 mayrepresent the final metal interconnect layer in an integrated circuit.It is to be appreciated that the above process operations may bepracticed in alternative sequences, not every operation need beperformed and/or additional process operations may be performed.Referring again to FIG. 7, self-aligned fabrication by the subtractiveapproach may be complete at this stage. A next layer fabricated in alike manner likely requires initiation of the entire process once again.Alternatively, other approaches may be used at this stage to provideadditional interconnect layers, such as conventional dual or singledamascene approaches.

Additionally, it is to be appreciated that the approaches described inassociation with FIGS. 6A-6G and 7 are not necessarily performed asforming vias aligned to an underlying metallization layer. As such, insome contexts, these process schemes could be viewed as involving blindshooting in the top down direction with respect to any underlyingmetallization layers. In another aspect, a subtractive approach providesalignment with an underlying metallization layer. Furthermore, a portionor remnant of a differentiated hardmask may be retained as a portion ofan inter-layer dielectric of a metallization layer. As an example ofboth such aspects, FIGS. 8A-8I illustrate portions of integrated circuitlayers representing various operations in a method of subtractiveself-aligned via patterning using electrobuckets with differentiatedhardmasks, in accordance with another embodiment of the presentinvention. In each illustration, at each described operation, an angledthree-dimensional cross-section view is provided.

FIG. 8A illustrates a starting point structure 800 for a subtractive viaprocess following deep metal line fabrication, in accordance with anembodiment of the present invention. Referring to FIG. 8A, structure 800includes metal lines 802 with intervening interlayer dielectric (ILD)lines 804. It is to be appreciated that some of the lines 802 may beassociated with underlying vias for coupling to a previous interconnectlayer. In an embodiment, the metal lines 802 are formed by patterningtrenches into an ILD material (e.g., the ILD material of lines 804). Thetrenches are then filled by metal and, if needed, planarized to the topof the ILD lines 804. In an embodiment, the metal trench and fillprocess involves high aspect ratio features. For example, in oneembodiment, the aspect ratio of metal line height (h) to metal linewidth (w) is approximately in the range of 5-10.

FIG. 8B illustrates the structure of FIG. 8A following recessing of themetal lines, in accordance with an embodiment of the present invention.Referring to FIG. 8B, the metal lines 802 are recessed selectively toprovide first level metal lines 806. The recessing is performedselectively to the ILD lines 804. The recessing may be performed byetching through dry etch, wet etch, or a combination thereof. The extentof recessing may be determined by the targeted thickness of the firstlevel metal lines 806 for use as suitable conductive interconnect lineswithin a back end of line (BEOL) interconnect structure.

FIG. 8C illustrates the structure of FIG. 8B following formation of aninter-layer dielectric (ILD) layer, in accordance with an embodiment ofthe present invention. Referring to FIG. 8C, an ILD material layer 808is deposited and, if necessary, planarized, to a level above therecessed metal lines 806 and the ILD lines 804.

FIG. 8D illustrates the structure of FIG. 8C following deposition andpatterning of a hardmask layer, in accordance with an embodiment of thepresent invention. Referring to FIG. 8D a hardmask layer 810 is formedon the ILD layer 808. In one such embodiment, the hardmask layer 810 isformed with a grating pattern orthogonal to the grating pattern of thefirst level metal lines 806/ILD lines 804, as is depicted in FIG. 8D. Inan embodiment, the grating structure formed by the hardmask layer 810 isa tight pitch grating structure. In one such embodiment, the tight pitchis not achievable directly through conventional lithography. Forexample, a pattern based on conventional lithography may first beformed, but the pitch may be halved by the use of spacer maskpatterning. Even further, the original pitch may be quartered by asecond round of spacer mask patterning. Accordingly, the grating-likepattern of the second hardmask layer 810 of FIG. 8D may have hardmasklines spaced at a constant pitch and having a constant width.

FIG. 8E illustrates the structure of FIG. 8D following trench formationdefined using the pattern of the hardmask of FIG. 8D, in accordance withan embodiment of the present invention. Referring to FIG. 8E, theexposed regions (i.e., unprotected by 810) of the ILD layer 808 areetched to form trenches 812 and patterned ILD layer 814. The etch stopson, and thus exposes, the top surfaces of the first level metal lines806 and the an lines 804.

FIG. 8F illustrates the structure of FIG. 8E following electrobucketformation in all possible via locations, in accordance with anembodiment of the present invention. Referring to FIG. 8F, first andsecond hardmask portions 897 and 899, respectively, are included inalternating locations of all possible via locations. A photoresist 816is then formed in all possible via locations above exposed portions ofthe recessed metal lines 806. The photoresist material 816 is includedin a plurality of electrobucket locations, of which locations 816A, 816Band 816C are depicted in FIG. 8F. Thus, three different possible vialocations 816A, 816B and 816C can be seen in the view provided in FIG.8F. Additionally, as depicted, the hardmask layer 810 may be removedfrom the patterned ILD layer 814.

In an embodiment, the first hardmask portions 897 are rendered ormodified to provide electrobuckets thereon with greater sensitivity toe-beam or UN exposure as compared to electrobuckets formed on the secondhardmask portions 899. In another embodiment, the second hardmaskportions 899 are rendered or modified to provide electrobuckets thereonwith less or reduced sensitivity to e-beam or EUV exposure as comparedto electrobuckets formed on the first hardmask portions 897. In eithercase, in an embodiment, the first hardmask portions 897 provide forincreased backscatter and the generation of more secondary electronsinto electrobuckets thereon versus the backscatter and the generation ofmore secondary electrons provided by second hardmask portions 899.

It is also to be appreciated that the photoresist layer 816 may notultimately be completely confined and separated in the electrobucketlocations. That is, in other embodiments, a photoresist layer is used asa continuous layer over a grating structure. In one embodiment, then,the photoresist 816 is formed above and over the top surfaces of the ILDlines 804, as is depicted in FIG. 8F.

FIG. 8G illustrates the structure of FIG. 8F following via locationselection, in accordance with an embodiment of the present invention.Referring to FIG. 8G, the electrobuckets 816A and 816C from FIG. 8F inselect via locations 818 are removed (i.e., electrobuckets 816A and 816Care removed). In locations where vias are not selected to be formed, thephotoresist 816 is retained (i.e., electrobucket 816B remains after thedevelopment process). In one embodiment, the photoresist 816 ofelectrobucket 816B is retained along with residual portions 816′. In oneembodiment, electrobucket 816B is at least partially exposed duringexposure of electrobuckets 816A and 816C. However, as described above,since the electrobucket 816B is not a select via location, thedifferentiated hardmask approach enables retention of electrobucket516B.

FIG. 8H illustrates the structure of FIG. 8G following conversion of theremaining electrobucket material, e.g., electrobucket 816B and, ifpresent, residual photoresist 816′, to permanent ILD material 820 and816″, respectively. Additionally, in an embodiment, the second hardmaskportion 899 is retained in the final structure as well. In anembodiment, the material of the remaining photoresist material ismodified, e.g., by cross-linking upon a baking operation, and may bereferred to as a cross-linked photolyzable material. In one suchembodiment, the final, cross-linked material has inter-dielectricproperties and, thus, can be retained in a final metallizationstructure. In an embodiment, the retained second hardmask portion 899 isdistinct from the retained cross-linked photolyzable material in that aseam or interface is observable in the final structure. However, inother embodiments, the electrobucket material of electrobucket 816B isnot converted to an ILD material and is instead ultimately removed andreplaced with a permanent ILD material. In one such embodiment, thesecond hardmask portion 899 is also removed.

Referring again to FIG. 8H, in an embodiment, the resulting structureincludes up to three different dielectric material regions (ILD lines804+ILD lines 814+cross-linked electrobucket 820, in one embodiment) ina single plane 850 of the metallization structure. In one suchembodiment, two or all of ILD lines 804, ILD lines 814, and cross-linkedelectrobucket 820 are composed of a same material. In another suchembodiment, ILD lines 804, ILD lines 814, and cross-linked electrobucket820 are all composed of different ILD materials. In either case, in aspecific embodiment, a distinction such as a vertical seam between thematerials of ILD lines 804 and ILD lines 814 (e.g., seam 897) and/orbetween ILD lines 804 and cross-linked electrobucket 820 (e.g., seam898) and/or between ILD) lines 814 and cross-linked electrobucket 820(e.g., seam 896) may be observed in the final structure.

FIG. 8I illustrates the structure of FIG. 8H following metal line andvia formation, in accordance with an embodiment of the presentinvention. Referring to FIG. 8I, metal lines 822 and vias 824 are formedupon metal fill of the openings of FIG. 8H. The metal lines 822 arecoupled to the underlying metal lines 806 by the vias 824. In anembodiment, the openings are filled in a damascene approach or abottom-up fill approach to provide the structure shown in FIG. 8I. Thus,the metal (e.g., copper and associated barrier and seed layers)deposition to form metal lines and vias in the above approach may bethat typically used for standard back end of line (BEOL) processing. Inan embodiment, in subsequent fabrication operations, the ILD lines 814may be removed to provide air gaps between the resulting metal lines824.

The structure of FIG. 8I may subsequently be used as a foundation forforming subsequent metal line/via and ILD layers. Alternatively, thestructure of FIG. 8I may represent the final metal interconnect layer inan integrated circuit. It is to be understood that the above processoperations may be practiced in alternative sequences, not everyoperation need be performed and/or additional process operations may beperformed. In any case, the resulting structures enable fabrication ofvias that are directly centered on underlying metal lines. That is, thevias may be wider than, narrower than, or the same thickness as theunderlying metal lines, e.g., due to non-perfect selective etchprocessing. Nonetheless, in an embodiment, the centers of the vias aredirectly aligned (match up) with the centers of the metal lines.Furthermore, the ILD used to select which plugs and vias will likely bevery different from the primary ILD and will be perfectly self-alignedin both directions. As such, in an embodiment, offset due toconventional lithograph/dual damascene patterning that must otherwise betolerated, is not a factor for the resulting structures describedherein. Referring again to FIG. 5I, then, self-aligned fabrication bythe subtractive approach may be complete at this stage. A next layerfabricated in a like manner likely requires initiation of the entireprocess once again. Alternatively, other approaches may be used at thisstage to provide additional interconnect layers, such as conventionaldual or single damascene approaches.

Overall, in accordance with one or more embodiments of the presentinvention, approaches described herein involve use of electrobucketinterlayer dielectric (ILD) to select locations for conductive vias. Thedetails above regarding FIGS. 2A-2O, 6A-6G, 7 and 8A-8I focus primarilyon electrobuckets used for via patterning. However, it is to beappreciated that electrobuckets including a selective grating approachmay also be used for dielectric plug patterning or line end patterning.

In an embodiment, the term “grating structure” or “pitch division” formetal lines, ILD lines or hardmask lines is used to refer to a tightpitch grating structure. In one such embodiment, the tight pitch is notachievable directly through conventional lithography. For example, apattern based on conventional lithography may first be formed, but thepitch may be halved by the use of spacer mask patterning, as is known inthe art. Even further, the original pitch may be quartered by a secondround of spacer mask patterning. Accordingly, the grating-like patternsdescribed above may have metal lines, ILD lines or hardmask lines spacedat a constant pitch and having a constant width. The pattern may befabricated by a pitch halving or pitch quartering approach.

In an embodiment, as used throughout the present description, interlayerdielectric (ILD) material is composed of or includes a layer of adielectric or insulating material. Examples of suitable dielectricmaterials include, but are not limited to, oxides of silicon (e.g.,silicon dioxide (SiO₂)), doped oxides of silicon, fluorinated oxides ofsilicon, carbon doped oxides of silicon, various low-k dielectricmaterials known in the arts, and combinations thereof. The interlayerdielectric material may be formed by conventional techniques, such as,for example, chemical vapor deposition (CVD), physical vapor deposition(PVD), or by other deposition methods.

In an embodiment, as is also used throughout the present description,interconnect material (e.g., metal lines and/or vias) is composed of oneor more metal or other conductive structures. A common example is theuse of copper lines and structures that may or may not include barrierlayers between the copper and surrounding ILD material. As used herein,the term metal includes alloys, stacks, and other combinations ofmultiple metals. For example, the metal interconnect lines may includebarrier layers (e.g., layers including one or more of Ta, TaN, Ti orTiN), stacks of different metals or alloys, etc. Thus, the interconnectlines may be a single material layer, or may be formed from severallayers, including conductive liner layers and fill layers. Any suitabledeposition process, such as electroplating, chemical vapor deposition orphysical vapor deposition, may be used to form interconnect lines. In anembodiment, the interconnect lines are composed of a conductive materialsuch as, but not limited to, Cu, Al, Ti, Zr, Hf, V, Ru, Co, Ni, Pd, Pt,W, Ag, Au or alloys thereof. The interconnect lines are also sometimesreferred to in the art as traces, wires, lines, metal, or simplyinterconnect.

In an embodiment, as is also used throughout the present description,plug and/or cap and/or hardmask materials are composed of dielectricmaterials different from the interlayer dielectric material. In oneembodiment, these materials are sacrificial, while interlayer dielectricmaterials are preserved at least somewhat in a final structure. In someembodiments, a plug and/or cap and/or hardmask material includes a layerof a nitride of silicon (e.g., silicon nitride) or a layer of an oxideof silicon, or both, or a combination thereof. Other suitable materialsmay include carbon-based materials. In another embodiment, a plug and/orcap and/or hardmask material includes a metal species. For example, ahardmask or other overlying material may include a layer of a nitride oftitanium or another metal (e.g., titanium nitride). Potentially lesseramounts of other materials, such as oxygen, may be included in one ormore of these layers. Alternatively, other plug and/or cap and/orhardmask material layers known in the arts may be used depending uponthe particular implementation. The plug and/or cap and/or hardmaskmaterial layers maybe formed by CVD, PVD, or by other depositionmethods.

It is to be appreciated that the layers and materials described aboveare typically formed on or above an underlying semiconductor substrateor structure, such as underlying device layer(s) of an integratedcircuit. In an embodiment, an underlying semiconductor substraterepresents a general workpiece object used to manufacture integratedcircuits. The semiconductor substrate often includes a wafer or otherpiece of silicon or another semiconductor material. Suitablesemiconductor substrates include, but are not limited to, single crystalsilicon, polycrystalline silicon and silicon on insulator (SOI), as wellas similar substrates formed of other semiconductor materials. Thesemiconductor substrate, depending on the stage of manufacture, oftenincludes transistors, integrated circuitry, and the like. The substratemay also include semiconductor materials, metals, dielectrics, dopants,and other materials commonly found in semiconductor substrates.Furthermore, the structures depicted above may be fabricated onunderlying lower level back end of line (BEOL) interconnect layers.

Embodiments disclosed herein may be used to manufacture a wide varietyof different types of integrated circuits and/or microelectronicdevices. Examples of such integrated circuits include, but are notlimited to, processors, chipset components, graphics processors, digitalsignal processors, micro-controllers, and the like. In otherembodiments, semiconductor memory may be manufactured. Moreover, theintegrated circuits or other microelectronic devices may be used in awide variety of electronic devices known in the arts. For example, incomputer systems (e.g., desktop, laptop, server), cellular phones,personal electronics, etc. The integrated circuits may be coupled with abus and other components in the systems. For example, a processor may becoupled by one or more buses to a memory, a chipset, etc. Each of theprocessor, the memory, and the chipset, may potentially be manufacturedusing the approaches disclosed herein.

FIG. 9 illustrates a computing device 900 in accordance with oneimplementation of an embodiment of the invention. The computing device900 houses a board 902. The board 902 may include a number ofcomponents, including but not limited to a processor 904 and at leastone communication chip 906. The processor 904 is physically andelectrically coupled to the board 902. In some implementations the atleast one communication chip 906 is also physically and electricallycoupled to the board 902. In further implementations, the communicationchip 906 is part of the processor 904.

Depending on its applications, computing device 900 may include othercomponents that may or may not be physically and electrically coupled tothe board 902. These other components include, but are not limited to,volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flashmemory, a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth).

The communication chip 906 enables wireless communications for thetransfer of data to and from the computing device 900. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 906 may implement anyof a number of wireless standards or protocols, including but notlimited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE,GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well asany other wireless protocols that are designated as 3G, 4G, 5G, andbeyond. The computing device 900 may include a plurality ofcommunication chips 906. For instance, a first communication chip 906may be dedicated to shorter range wireless communications such as Wi-Fiand Bluetooth and a second communication chip 906 may be dedicated tolonger range wireless communications such as GPS, EDGE, GPRS, CDMA,WiMAX, LTE, Ev-DO, and others.

The processor 904 of the computing device 900 includes an integratedcircuit die packaged within the processor 904. In some implementationsof embodiments of the invention, the integrated circuit die of theprocessor includes one or more structures, such as conductive viasfabricated using an approach based on electrobuckets havingdifferentiated underlying hardmasks, built in accordance withimplementations of embodiments of the invention. The term “processor”may refer to any device or portion of a device that processes electronicdata from registers and/or memory to transform that electronic data intoother electronic data that may be stored in registers and/or memory.

The communication chip 906 also includes an integrated circuit diepackaged within the communication chip 906. In accordance with anotherimplementation of an embodiments of the invention, the integratedcircuit die of the communication chip includes one or more structures,such as conductive vias fabricated using an approach based onelectrobuckets having differentiated underlying hardmasks, in accordancewith embodiments of the invention.

In further implementations, another component housed within thecomputing device 900 may contain an integrated circuit die that includesone or more structures, such as conductive vias fabricated using anapproach based on electrobuckets having differentiated underlyinghardmasks, in accordance with embodiments of the invention.

In various implementations, the computing device 900 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, the computingdevice 900 may be any other electronic device that processes data.

FIG. 10 illustrates an interposer 1000 that includes one or moreembodiments of the invention. The interposer 1000 is an interveningsubstrate used to bridge a first substrate 1002 to a second substrate1004. The first substrate 1002 may be, for instance, an integratedcircuit die. The second substrate 1004 may be, for instance, a memorymodule, a computer motherboard, or another integrated circuit die.Generally, the purpose of an interposer 1000 is to spread a connectionto a wider pitch or to reroute a connection to a different connection.For example, an interposer 1000 may couple an integrated circuit die toa ball grid array (BGA) 1006 that can subsequently be coupled to thesecond substrate 1004. In some embodiments, the first and secondsubstrates 1002/1004 are attached to opposing sides of the interposer1000. In other embodiments, the first and second substrates 1002/1004are attached to the same side of the interposer 1000. And in furtherembodiments, three or more substrates are interconnected by way of theinterposer 1000.

The interposer 1000 may be formed of an epoxy resin, afiberglass-reinforced epoxy resin, a ceramic material, or a polymermaterial such as polyimide. In further implementations, the interposermay be formed of alternate rigid or flexible materials that may includethe same materials described above for use in a semiconductor substrate,such as silicon, germanium, and other group III-V and group IVmaterials.

The interposer may include metal interconnects 1008 and vias 1010,including but not limited to through-silicon vias (TSVs) 1012. Theinterposer 1000 may further include embedded devices 1014, includingboth passive and active devices. Such devices include, but are notlimited to, capacitors, decoupling capacitors, resistors, inductors,fuses, diodes, transformers, sensors, and electrostatic discharge (ESD)devices. More complex devices such as radio-frequency (RF) devices,power amplifiers, power management devices, antennas, arrays, sensors,and MEMS devices may also be formed on the interposer 1000. Inaccordance with embodiments of the invention, apparatuses or processesdisclosed herein may be used in the fabrication of interposer 1000 or inone or more of the components of the interposer 1000.

Thus, embodiments of the present invention include approaches based ondifferential hardmasks for modulation of electrobucket sensitivity forsemiconductor structure fabrication, and the resulting structures.

Example embodiment 1: A method of fabricating an interconnect structurefor an integrated circuit includes forming a hardmask layer above aninter-layer dielectric (ILD) layer formed above a substrate. A pluralityof dielectric spacers is formed on the hardmask layer. The hardmasklayer is patterned to form a plurality of first hardmask portions. Aplurality of second hardmask portions is formed alternating with thefirst hardmask portions. A plurality of electrobuckets is formed on thealternating first and second hardmask portions and in openings betweenthe plurality of dielectric spacers. Electrobuckets formed on the firsthardmask portions have a different sensitivity to e-beam or extremeultra-violet (EUV) radiation than electrobuckets formed on the secondhardmask portions. Select ones of the plurality of electrobuckets areexposed to a lithographic exposure and removed to define a set of vialocations.

Example embodiment 2: The method of example embodiment 1, wherein theelectrobuckets formed on the first hardmask portions have lesssensitivity to the e-beam or EUV radiation than the electrobucketsformed on the second hardmask portions.

Example embodiment 3: The method of example embodiment 1, wherein theelectrobuckets formed on the first hardmask portions have greatersensitivity to the e-beam or EUV radiation than the electrobucketsformed on the second hardmask portions.

Example embodiment 4: The method of example embodiment 1, 2 or 3,wherein the electrobuckets formed on the first hardmask portions havedifferent sensitivity to the e-beam or EUV radiation than theelectrobuckets formed on the second hardmask portions based on adifference in the extent of backscatter and generation of secondaryelectrons between the first hardmask portions and the second hardmaskportions.

Example embodiment 5: The method of example embodiment 1, 3 or 4,further including etching the set of via locations into the ILD layer.Subsequent to etching the set of via locations into the ILD layer, aplurality of metal lines is formed in the ILD layer, where select onesof the plurality of metal lines include an underlying conductive viacorresponding to the set of via locations.

Example embodiment 6: The method of example embodiment 1, 2, 3, 4 or 5,wherein the second hardmask portions are formed by filling pores in aporous dielectric layer with a metal-containing material.

Example embodiment 7: The method of example embodiment 1, 2, 3, 4 or 5,wherein the second hardmask portions are formed by oxidizing ametal-containing material.

Example embodiment 8: The method of example embodiment 1, 2, 3, 4, 5, 6or 7, wherein the exposing and removing select ones of the plurality ofelectrobuckets involves removing electrobuckets formed on the secondhardmask portions but not removing electrobuckets formed on the firsthardmask portions.

Example embodiment 9: The method of example embodiment 1, 2, 4, 5, 6, 7or 8, wherein one or more of the electrobuckets formed on the firsthardmask portions are exposed to the e-beam or EUV radiation but are notremoved during the removing of the select ones of the plurality ofelectrobuckets.

Example embodiment 10: The method of example embodiment 1, 2, 3, 4, 5,6, 7, 8 or 9, wherein exposing and removing the select ones of theplurality of electrobuckets to define the set of via locations includesremoving corresponding second hardmask portions.

Example embodiment 11: The method of example embodiment 10, furtherincluding modifying remaining second hardmask portions, forming a secondplurality of electrobuckets, exposing and removing select ones of theelectrobuckets formed on the first hardmask portions but not removingelectrobuckets formed on the modified second hardmask portions to definea second set of via locations.

Example embodiment 12: The method of example embodiment 11, furtherincluding etching the set of via locations and the second set of vialocations into the ILD layer. Subsequent to etching the set of vialocations and the second set of via locations into the ILD layer, aplurality of metal lines is formed in the ILD layer, where select onesof the plurality of metal lines include an underlying conductive viacorresponding to the set of via locations and to the second set of vialocations.

Example embodiment 13: The method of example embodiment 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 11 or 12, wherein forming the plurality of dielectricspacers involves forming a grating structure using a pitch divisionprocessing scheme.

Example embodiment 14: An interconnect structure for an integratedcircuit includes a first layer of the interconnect structure disposedabove a substrate, the first layer including a first grating ofalternating metal lines and dielectric lines in a first direction. Thedielectric lines have an uppermost surface higher than an uppermostsurface of the metal lines. A second layer of the interconnect structureis disposed above the first layer of the interconnect structure. Thesecond layer includes a second grating of alternating metal lines anddielectric lines in a second direction, perpendicular to the firstdirection. The dielectric lines have a lowermost surface lower than alowermost surface of the metal lines of the second grating. Thedielectric lines of the second grating overlap and contact, but aredistinct from, the dielectric lines of the first grating. A region ofdielectric material is disposed between the metal lines of the firstgrating and the metal lines of the second grating, and in a same planeas upper portions of the dielectric lines of the first grating and lowerportions of the dielectric lines of the second grating. The region ofdielectric material includes a cross-linked photolyzable materialdisposed on a distinct underlying hardmask portion.

Example embodiment 15: The interconnect structure of example embodiment14, wherein the cross-linked photolyzable material is a photo-acidgenerator (PAG)-based cross-linked photolyzable material.

Example embodiment 16: The interconnect structure of example embodiment14 or 15, further including a conductive via disposed between andcoupling a metal line of the first grating to a metal line of the secondgrating, the conductive via in the same plane as the region ofdielectric material.

Example embodiment 17: The interconnect structure of example embodiment16, wherein the conductive via has a center directly aligned with acenter of the metal line of the first grating and with a center of themetal line of the second grating.

Example embodiment 18: The interconnect structure of example embodiment14, 15, 16 or 17, wherein the dielectric lines of the first gratinginclude a first dielectric material, and the dielectric lines of thesecond grating include a second, different dielectric material, andwherein the first and second dielectric materials are different than thecross-linked photolyzable material.

Example embodiment 19: The interconnect structure of example embodiment14, 15, 16 or 17, wherein the dielectric lines of the first grating andthe dielectric lines of the second grating include a same dielectricmaterial different than the cross-linked photolyzable material.

Example embodiment 20: A method of fabricating an interconnect structurefor an integrated circuit includes forming a mask above an ILD materiallayer, the mask having a plurality of spaced apart features each with acentral portion and a pair of sidewall spacers. The method also includesforming, using the mask, a first plurality of trenches partially intothe ILD material layer. The method also includes forming first hardmaskportions and a first plurality of electrobuckets in the first pluralityof trenches. The method also includes forming a second mask from themask by removing the central portion of each feature of the mask. Themethod also includes forming, using the second mask, a second pluralityof trenches partially into the ILD material layer. The method alsoincludes forming second hardmask portions and a second plurality ofelectrobuckets in the second plurality of trenches, wherein the secondplurality of electrobuckets has less sensitivity to e-beam or extremeultra-violet (EUV) radiation than the first plurality of electrobuckets.The method also includes exposing, developing and removing fewer thanall of the first plurality of electrobuckets by using a lithographicexposure. The method also includes forming via locations where the fewerthan all of the first electrobuckets were remove& and forming metal viasin the via locations and metal lines above the metal vias.

Example embodiment 21: The method of example embodiment 20, wherein thefirst plurality of electrobuckets and the second plurality ofelectrobuckets are formed from a same photoresist material.

Example embodiment 22: The method of example embodiment 20 or 21,wherein the exposing involves at least partially exposing portions ofthe second plurality of electrobuckets, but the developing and removingdoes not remove the exposed portions of the second plurality ofelectrobuckets.

Example embodiment 23: The method of example embodiment 20, 21 or 22,wherein the first hardmask portions have a greater extent of backscatterand generation of secondary electrons than the second hardmask portions.

What is claimed is:
 1. An interconnect structure for an integratedcircuit, the interconnect structure comprising: a first layer of theinterconnect structure disposed above a substrate, the first layercomprising a first grating of alternating metal lines and dielectriclines in a first direction, wherein the dielectric lines have anuppermost surface higher than an uppermost surface of the metal lines;and a second layer of the interconnect structure disposed above thefirst layer of the interconnect structure, the second layer comprising asecond grating of alternating metal lines and dielectric lines in asecond direction, perpendicular to the first direction, wherein thedielectric lines have a lowermost surface lower than a lowermost surfaceof the metal lines of the second grating, wherein the dielectric linesof the second grating overlap and contact, but are distinct from, thedielectric lines of the first grating; and a region of dielectricmaterial disposed between the metal lines of the first grating and themetal lines of the second grating, and in a same plane as upper portionsof the dielectric lines of the first grating and lower portions of thedielectric lines of the second grating, the region of dielectricmaterial comprising a cross-linked photolyzable material disposed on adistinct underlying hardmask portion, wherein the distinct underlyinghardmask portion includes a porous dielectric material comprising poresfilled with a metal-containing material.
 2. The interconnect structureof claim 1, wherein the cross-linked photolyzable material is aphoto-acid generator (PAG)-based cross-linked photolyzable material. 3.The interconnect structure of claim 1, further comprising: a conductivevia disposed between and coupling a metal line of the first grating to ametal line of the second grating, the conductive via in the same planeas the region of dielectric material.
 4. The interconnect structure ofclaim 3, wherein the conductive via has a center directly aligned with acenter of the metal line of the first grating and with a center of themetal line of the second grating.
 5. The interconnect structure of claim1, wherein the dielectric lines of the first grating comprise a firstdielectric material, and the dielectric lines of the second gratingcomprise a second, different dielectric material, and wherein the firstand second dielectric materials are different than the cross-linkedphotolyzable material.
 6. The interconnect structure of claim 1, whereinthe dielectric lines of the first grating and the dielectric lines ofthe second grating comprise a same dielectric material different thanthe cross-linked photolyzable material.